156 lines
7.5 KiB
HTML
156 lines
7.5 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<HTML>
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<HEAD>
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<title>Adventures with PPP Issue 21</title>
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</HEAD>
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<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#0020F0"
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ALINK="#FF0000">
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<H4>
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"Linux Gazette...<I>making Linux just a little more fun!</I>"
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</H4>
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<P> <HR> <P>
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<!--===================================================================-->
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<center>
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<H2>Adventures with PPP</H2>
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<H4>By Larry Ayers,
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<a href="mailto:layers@marktwain.net">layers@marktwain.net</a></H4>
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</center>
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<P><HR><P>
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<center><h3>Introduction</h3></center>
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<p>When I first began using Linux a couple of years ago, one of my goals was
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to be able to go on-line. At that time I was constantly rebooting into OS/2
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so I could use the internet and this OS schizophrenia was becoming tiresome.
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<p>Eventually, after many chatscript iterations and minicom sessions I had a
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dependable PPP setup. I thought my PPP troubles were over; as time passed my
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command of the various <i>pppd</i> and <i>chat</i> options began to fade.
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<p>This past month my local internet service provider sold its machines and
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signed up with a large provider in Atlanta. When the accounts were switched
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over suddenly I could no longer log in and life became a bit too
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interesting...
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<center><h3> Log-In Fashions Change</h3></center>
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<p>A couple of years ago an ISP was happy just to have a set of working log-in
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scripts which could be distributed to its Windows and Mac customers. At that
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time most computer users were either hobbyists or professionals, and could be
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counted on to know what to do with the script. As the internet surged in
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popularity more and more customers appeared without much knowledge of basic
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computer usage, and the help-desks and support personnel began to be swamped
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with requests for set-up help. Naturally, the tendency was to move towards
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simpler log-in set-ups, if possible without any script at all. As customer interest in
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text-mode shell accounts waned, a log-in could be accomplished with little
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more than the username and password. This (I was informed in an e-mail from
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my provider) was our new log-in sequence: just the username and password.
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<p>This sounded simple enough; all I had to do was delete the expect-send
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sequence <kbd>selection: PPP</kbd> from the chat-script and all
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would be well. Or so I thought: using this script led to a scrolling list of
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errors on the console I set up to display all daemon and error messages. It
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looked like the router I was attempting to connect to was first trying PAP
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authentication, failing, then trying CHAP authentification, failing that as well;
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the sequence would repeat until the router would hang up in disgust.
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<p>Other variations of the chat-script I tried would result in a "serial line
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not 8-bit clean" message. I talked with the technician who had set up the
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local router and he claimed that neither PAP nor CHAP were in use; Win95
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log-ins were working fine, so I was on my own.
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<p>The next step was to try logging in with Minicom, just to see what the
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actual log-in screen looked like. I connected and found the expected <kbd>Username:</kbd>
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and <kbd>Password:</kbd> prompts. I logged in and a command prompt appeared, with
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no sign of the typical PPP garbage characters. What now? I typed
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<b>help</b> and a list of available commands scrolled by. I was logged in
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to the Cisco router, evidently, and before long I found that I could telnet
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anywhere I liked. I could run a <kbd>systat</kbd> command and see which other
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users were logged in. The command <kbd>show hosts</kbd> provided a list of
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hosts which I could connect to, and soon I was logged in at the main
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WWW server in Atlanta! I'd never been logged in at an UltraSparc server
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running Unix SysVR4 before, and it was great fun exploring the directory
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structure and running real VI for the first time. I could run pine (and I
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ended up with yet another e-mail address) and read news with the nn
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newsreader.
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<p>This was all quite diverting, but didn't address the PPP problem. So soon
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I was back at the router's prompt. I tried typing <kbd>ppp</kbd> and the
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indicative garbage characters appeared. This looked encouraging, so I added
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this exchange to my chatscript and tried again. The <i>pppd</i> daemon was
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satisfied this time, and I had what looked like a real PPP session.
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Unfortunately, it turned out to be limited to the router and I could do
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nothing with the connection. Another dead-end!
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<center><h3>Back to OS/2</h3></center>
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<p>At first I couldn't even log in with OS/2 when I revived an old installation and
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tried to dial in. Deleting the entire log-in sequence in the dialer got me
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online again, but even with debugging turned on I still couldn't determine
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just when the username and password strings were being sent to the server.
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<p>On-line once again, I was off to the newsgroups hoping to find advice.
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<p>Eventually I came across a posting in <i>comp.os.linux.networking</i> which
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contained a couple of intriguing statements. The first intimated that Win95
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by default makes use of PAP authentification, but the user isn't necessarily
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informed of the fact. Possibly the Netscape dialer which my ISP distributes
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was using PAP as well, I thought. The second statement recommended using the
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<i>pppd</i> option <kbd>+ua /etc/ppp/pap-secrets</kbd>. I had seen this
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option while reading the <i>pppd</i> <kbd>/etc/ppp/options</kbd> file, but the manual
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listed this option as being obsolete, so I'd never tried it.
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<p>The posting's author recommended an unusual format for the
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<kbd>pap-secrets</kbd> file, unlike the format recommended in the
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documentation I'd been reading and unlike the sample included in my PPP
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installation: just a simple two-line file, the first line containing the
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username and the second displaying the password. No server or client names,
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just the two words.
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<center><h3>Success</h3></center>
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<p>I was surprised and elated when this configuration worked the first time.
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I had the chat-script simply dial the number and wait for the
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<kbd>CONNECT</kbd> string. The server asked for PAP authentification and I
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was online without even dealing with the username and password prompts, which
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I suppose are only for the maintainers of the router.
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<p>I'm writing this piece because I suspect that many other servers will
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probably be adopting similar streamlined login procedures, and the approach
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I've outlined here may prove useful in at least some of these cases. One
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thing to remember is that directing the <kbd>pppd</kbd> debugging messages to
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an unused virtual console is very helpful, most easily accomplished by
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inserting the line:<br>
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<p>
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<kbd>*.* /dev/tty8</kbd><br>
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<p>in your <tty>/etc/syslog.conf</tty> file.
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<!--===================================================================-->
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<P> <hr> <P>
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<center><H5>Copyright © 1997, Larry Ayers<BR>
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Published in Issue 21 of the Linux Gazette, September 1997</H5></center>
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